Generally, the term “display device” comprehensively refers to monitors for TV, computers, or the like, and includes a display assembly containing a display panel for forming image, and a casing for supporting the display assembly.
The display assembly includes a display panel such as CRT (Cathode Ray Tube), LCD (Liquid Crystal Display) and PDP (Plasma display Panel) for forming image, a circuit board for driving the display panel and an optical filter disposed in front of the display panel.
The optical filter comprises an anti-reflection film for preventing the external light incident from the outside from be reflected outward again, a near infrared ray shielding film for shielding the near infrared ray generated in the display panel for prevention of misoperation of an electronic instrument such as a remote controller, a color correction film for enhancing the color purity through control of the shade by incorporation of a color adjusting dye, and an EMI (electromagnetic interference) shielding film for shielding the EMI (electromagnetic interference) generated in the display panel upon driving the display device.
As used herein, the EMI (electromagnetic interference) shielding film comprises a substrate made from transparent materials, and a conductive pattern made from metallic materials patterned by a photolithography process, having excellent electric conductivity such as silver and copper.
Since the conductive pattern is provided with high-gloss metal materials, light incident from the outside is reflected, or the image light from the display panel is reflected, which may cause reduction of the contrast ratio. As such, in order to inhibit such effect, the surface of the conductive pattern is generally subject to blackening processing. That is, the conductive pattern is usually blackened.
As a blackening processing for a conductive pattern, KR Patent Application Publication No. 2004-0072993 discloses a process for blackening processing of a mesh using chemicals such as concentrated nitric acid after forming the mesh on a metal foil by photolithography.
Further, Japanese Patent Application Publication No. 2001-210988 discloses a process for blackening processing of the surface of a mesh formed by photolithography, using concentrated nitric acid.
However, these processes for blackening processing of a conductive pattern have problems that after forming a conductive pattern, the conductive pattern is required to be treated with concentrated nitric acid, leading to deteriorated workability.
Moreover, if the conductive pattern is blackened, there are provided problems that the processing time is too long, and that sufficient degree of blackness cannot be obtained. Further, there is also a problem that the sheet resistance of the conductive pattern affecting the ability of shielding the EMI (electromagnetic interference) is increased.